The present invention relates to test methods and apparatus, and more particularly to a test procedure and testing apparatus for the manufacturing control of electrical drives with low output RPM. Such drives may, for instance, be of the type used for automotive window lifters and provided with a high ratio reduction gear. In one previously-used approach, the free end of a rope or cable carrying a weight is wound around a pulley in the direction of rotation, as many times as is needed, making use of friction between the surface of the pulley and the rope to establish a load. When testing the drive in the opposite direction, the direction in which the rope is wound must be changed accordingly.
In the previously used procedure, measurement of drive current has been carried out with commercially available ammeters; the low output RPM has been checked with hand tachometers and the direction of rotation monitored by visual inspection. For measuring torque, a rope was attached to a fixed spring scale and the free end wound around the surface of the pulley at the running test as many times as was necessary to produce sufficient friction to stop the rotation of the pulley. The force on the spring scale was then read and the braking torque calculated. As much of it is manual, such a procedure is inherently slow and subject to inaccuracy. Accordingly, it will be seen that it would be advantageous to render the testing of electrical drives with low output RPM as extensively automatic as possible and without loss of time.
It is therefore an object of the invention to provide an improved means and method for the testing of low-speed electrical drives.
It is another object of the invention to provide an efficient and automatic means for testing low-speed drives including high ratio gear reduction systems.